This invention relates to thin film coating deposition systems of the vacuum coating type generally and more particularly to improved winding configurations used with roll coaters for use in vacuum coating systems, especially in sputtering vacuum coating systems. This application also discloses a computer program which controls the process of depositing a coating on flexible material used in the apparatus.
Vacuum coating deposition of thin films covers a broad class of coating processes in which material is removed from a source and deposited on a substrate, the process being carried out in a vacuum or partial vacuum. For example, when one considers vapor deposition one will include chemical vapor deposition in which gaseous chemical compounds react and deposit on heated substrates. In ion vapor deposition, an inert or plasma forming gas is ionized and a high negative potential is applied to the substrate or material to be coated. The coating metal is melted and vaporized then ionized to accomplish the coating procedure.
Lastly, there is physical vapor deposition in which material is physically removed from a source by evaporation or sputtering, transported through a vacuum or partial vacuum by the energy of the vapor particles and condensed as deposited coating or a film on the surface of a material. A myriad of physical vapor processes are known including diode or triode sputtering planar or cylindrical magnetron sputtering, direct current or radio frequency sputtering, electron beam evaporation, activated reactive evaporation and arc evaporation. This invention most specifically relates to sputtering and will be specifically described with reference thereto.
When rolls of flexible substrate material are to be coated by vacuum deposition, the process is referred to as "roll coating". This invention most specifically relates to roll coating. Typically, rolls of polyester or polyimide are used as flexible substrates in roll coating although a wide variety of other roll materials may be used including other plastic films, metallized papers, fabrics and even sheet metals. The improved roll coater and winding configuration of the invention is broadly applicable for use in all of the various vacuum coating procedures including chemical vapor deposition and ion vapor deposition as well as physical vapor deposition processes. However, it is described herein particularly with respect to the sputtering process as applied to roll coating.
In a typical roll coater, a roll of flexible substrate material, also known as a web, is carried on a feed roll. The substrate is threaded or led through various idler, drive and tension control rolls, passed through the coating region and taken up on a take-up roll after being coated. The apparatus is operated in a vacuum chamber.
A pumping system evacuates the vacuum chamber to a low pressure, for example approximately 1.0.times.10.sup.-6 torr or so. After evacuation is attained the chamber is backfilled with a plasma forming gas, typically, argon, to a pressure of 2.0.times.10.sup.-3 torr or so.
In roll sputtering, as in the preferred embodiments of this invention, the flexible substrate passes through a cloud of charged particles at a specific rate. Positively charged ions in a plasma (cloud of charged particles) strike a negatively biased source target, causing metal atoms to be ejected from the target toward the substrate surface. The ejected metal atoms strike and adhere to the substrate, forming a thin coating. After the entire roll is coated, the vacuum chamber is opened and the coated roll is removed.